UK light heavyweight Buatsi earned a win yet disappointing start to his career under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a majority decision in a competitive 10-round contest at the Manchester venue.
But Parker landed significant shots, connecting with powerful individual punches in a contest where the approaches failed to mesh, with constant grabbing disrupting the contest.
Two judges scored it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my finest showing but what do champions do? They succeed," Buatsi stated in the ring as he was met by disapproval from the spectators.
The British fighter bounced back after his first professional defeat - an memorable fight with his previous opponent in February - to claim a twentieth professional win.
Several boxing experts felt the challenger, thirty-one, deserved the win but the contender endured the second defeat of his 28-fight professional journey.
The Champion Claims Triumph in Dull Encounter
His career development has stalled in the past few years through management issues and extended periods of inactivity.
Earlier forecast as the next star of UK boxing, he now finds himself trying to fulfil that early promise - possibly in what seems like a ultimate opportunity - under recent support.
He began cautiously, with neither fighter prepared to overcommit in a cagey initial rounds.
Parker, whose single earlier setback came at super-middleweight against his former opponent in two years ago after breaking his hand during the bout, was competing in only his second appearance at light-heavyweight.
By the middle rounds, Parker had made it competitive, creating difficulties for Buatsi, who utilized a protective stance to edge the better periods.
The spectators' acceptance decreased during constant clinching, with Parker going down various instances during grappling.
The underdog finished the stronger, but several stanzas were challenging to assess. Although, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for Parker, awarding Buatsi just one round.
The victor advances, but with the likes of hard hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still looks steep.
Ricky Hatton Tribute Motivates All-Manchester Contest
In the secondary fight, Arthur beat Rea by close verdict in a outstanding Manchester vs Manchester battle to secure the European light heavyweight title.
The venue fell silent for a deeply poignant tribute before the fight as a bell ceremony rang in remembrance of the city's native Hatton, who passed away at age 46 in September.
It was the initial significant broadcast match card in the urban center since Hatton's death. As the final chime faded, the silence transitioned to a roar of "there's only one Hatton".
The competition inside the ropes matched the sentiment. Arthur was floored by a left hook directly to the face in the initial stage, rising shakily to his position on the eight count.
But the Manchester United-red attire of the fighter soon pressed ahead again. On the opposite side, the opponent - in competitive blue - was injured early, heavy swelling appearing under his eye as the pair traded punishing blows.
Rea, twenty-seven, connected with strong blows but the champion, thirty-four, matched the intensity with effective uppercuts as the intensity hardly diminished over the full distance.
Arthur narrowly won the verdict with judges scorecards of even score, 115-113 and wider gap, but the two athletes were relentless and brave, exactly what their hero the legend represented.
